After a tough first inning in which he allowed four runs (zero earned runs) against the New York Yankees, Luis Severino went out to warm up for the second inning, and just didn't feel right. He would end up leaving the game after one inning with what was later deemed right arm soreness.

He mentioned that he'd been dealing with the soreness since his last start against the Angels. As he was warming up before the second inning, his arm was just getting tighter and tighter the more he threw. 

After the injury to Aaron Civale on Monday, the A's called up Gage Jump to start the following day, despite Severino being lined up for the Seattle start. Then the righty was pushed back to Friday's game against the Yankees. On the surface, this just looked like the A's trying to take advantage of the Mariners' struggles against left-handers, while giving Severino a big-game scenario to thrive in. 

After the game, Martín Gallegos reported that Severino would be undergoing further tests on Saturday. The righty also said of making his next start: "The biggest [worry] is finding something that keeps me out a long time. If worst case scenario is I miss one or two starts, I’m happy with that."

Reading between the lines — and admittedly speculating — this seems to be an admission that Severino expects to miss a start or two at the very least. How long he ends up being out depends upon the prognosis he receives on Saturday. 

We won't know what steps the A's will be taking until those tests happen, but we can assess a couple of different paths forward for the club in the short term. 

The production and the ability to eat innings won't be easy to replace for the green and gold. His 62 2/3 innings in 12 starts — including Friday's one inning affair — ranks second on the club behind Jeffrey Springs in his 12 starts. Civale, another veteran, ranked third with 55 2/3 innings in 11 starts. 

All three starters were racking up innings and putting up ERAs between 4.07 and 4.20. Now one of those pieces is on the IL in Civale, with another potentially joining him in Severino. 

With the A's off-day on Monday in Chicago, that could open up the A's to roll with a four-man rotation — Jump, Springs, J.T. Ginn and Jacob Lopez. 

The way things shake out right now, Jump would get the start on Tuesday, June 2, with Springs and Ginn behind him on regular rest to finish off the series with the Cubs. Lopez, with or without an opener, would be in line for Friday's start in Houston on regular rest as well. It wouldn't be until Saturday against the Astros where the schedule would catch up with them.

Depending on how the tests go, this could be enough time to get Severino back for a start. If the injury is more serious and requires an IL stint, the A's could still utilize the four-man rotation to line up the starter they prefer at the time they want. 

One big option could be Jack Perkins, who ate 4 2/3 innings against the Mariners on Monday and was able to throw 63 pitches. This could be the best shot the righty may have to earn a spot in the rotation. He seems like the most likely option as well.

The only real downside would be that he has a decent amount of MLB experience now, and that could also be used as a backup option to create a bridge between a faltering starter and the back-end of the bullpen. The answer likely depends on the severity of Severino's injury. If he's out longer, Perkins could be the guy. 

Luis Morales started the season in the A's rotation, but after two starts to begin the year and a relief appearance in May, the young righty holds a 14.46 ERA across 9 1/3 innings. His biggest issue has been walks, and those have come under control a little more since May 10. 

In six outings spanning 9 1/3 relief innings, Morales has given up 10 hits, walked three and struck out 11. He's also given up seven earned runs in that span. The overall results aren't there, but the process appears to be taking a step forward. He is on the 40-man roster already, and could be a relief option to take Perkins' place if needed. 

Mason Barnett is another option to consider, and he may be the one the A's turn to in either a starting or a relief role, given that he's made a couple of trips up to the big leagues this season to eat innings already. The biggest downside for Barnett is that he allowed six walks in back-to-back starts on May 16 and May 22. 

Those two outings have hurt his overall numbers on the season, with the righty holding a 4.64 ERA with a 1.52 WHIP. He'd held a 3.07 ERA with a 1.26 WHIP heading into that first game. 

Joey Estes is the only one of this trio that has yet to see big-league time this season, though he has the most MLB experience of the group. Across 53 innings in 11 starts, Estes holds a 5.94 ERA with a 1.53 WHIP. 

The answer to who will end up getting a starting role (if necessary) will be the pitcher the A's feel gives them the best shot at recording some innings for the club either in the rotation or in a relief role. 

This is a key stretch for the club, where the front office is evaluating in-house options before turning to the trade market in July. This will either be a time where the internal options step up, and provide the boost the A's need, or this could be the point in the year when the season starts to slip away. 

If Luis Severino is set to miss time, who are you putting into the rotation? Join AthleticsRoundtable — it's free — and let us know who's taking the ball every fifth day in your rotation. Never miss an article by following Jason @ByJasonB!